1. Field of Invention
This invention relates generally to tapes for sealing cartons, packages and other articles, and more particularly to a fiberglass-reinforced sealing tape for this purpose having a paper inner ply and a synthetic plastic film outer ply laminated thereto by a water-based adhesive, the outer ply being strippable from the inner ply so that the article can be recycled.
2. Status of Prior Art
Because of rising environmental concerns, in recent years stress has been placed on the use of products fabricated of materials which can be recycled. Thus a strong preference now exists for bags, cartons and other articles made of paper, for these articles can then be recycled. This is not true of most products made entirely or in part of synthetic plastic materials.
Thus a corrugated board carton lends itself to recycling, but not if the carton has a synthetic plastic film liner to render it water-resistant. A similar problem is encountered when use is made of a standard fiberglass-reinforced paper tape to seal the carton. This tape has its inner and outer paper plies laminated together by a hot melt polymeric adhesive, the nature of which is such that it is not compatible with recycling operations.
In recycling, the carton is shredded in a beater and a slurry is then formed of the shredded material for further processing. While metal staples, glass fibers and other foreign objects may readily be filtered out of the slurry, a hot melt polymeric adhesive cannot, and this contaminates the slurry. Hence a standard, fiberglass-reinforced paper tape, when used to seal an otherwise recyclable article, usually renders it non-recyclable, unless the tape is first stripped off. But to do so is a time consuming and difficult operation, for the gummed face of the tape is securely joined to the article and should one seek to strip this tape from the article, a residue of hot melt adhesive remains thereon and renders it unsuitable for recycling.
In a standard fiberglass-reinforced sealing tape, two plies of Kraft paper, laminated together by a hot melt adhesive, have sandwiched therebetween two superposed arrays of fiberglass strands. In one array, parallel strands of fiberglass run longitudinally alone the tape, while in the other, the parallel strands run in the cross direction at an angle to the longitudinal strands. The resultant thickness of the tape is such that when it is wound into a roll having a 7 inch diameter for use in a conventional manually or electrically-operated tape dispenser, the tape capacity of the roll is relatively low. Clearly, this thinner the tape, the greater is the yardage of tape contained in a 7 inch diameter roll. But with a relatively thick laminated paper tape having two arrays of fiberglass sandwiched between its plies, the limited yardage in a roll of this tape gives rise to practical problems.
Thus when the tape dispenser is in uninterrupted use in sealing operations for mass-produced cartons, the tape roll is quickly exhausted, thereby making it necessary to put a fresh roll in the dispenser at frequent intervals. And because the hot melt adhesive in the tape tends to build up on the cutting blade of the dispenser, it is necessary from time to time to shut down the dispenser to clean this blade. And because each 7 inch diameter tape roll contains a limited yardage of tape, the storage space required for an adequate stock of such tape is high.
Moreover, when the paper/paper sealing tape is used to seal and hold together a carton that in the course of shipment becomes exposed to rain or snow, the paper tape will absorb water which may leak into the carton. And the wet tape may be so weakened as to cause it to give way, with a resultant collapse of the carton.
But quite apart from the drawbacks of a standard reinforced paper/paper tape in the context of tape dispensers are the problems encountered when manufacturing a tape of this type in a conventional laminator. In manufacturing, two Kraft paper webs are continuously fed into the laminator, the surface of one web having first applied thereto a coating of hot melt adhesive. Also continuously fed into the laminator are the longitudinal and cross arrays of fiberglass strands. The need to feed separate arrays of fiberglass strands into the laminator dictates a relatively slow operating speed, with a resultant low tape production rate per hour.
Also, the hot melt adhesive must be maintained in a heated state while the laminator is in operation. And because this hot, flowable adhesive tends to drip over the operating mechanism of the laminator, it becomes necessary from time to time to shut down the laminator and use solvents to clean it. The use of volatile solvents may lead to troublesome environmental problems.